(1) Field of the Invention
The present invention pertains to a manually operated reciprocating liquid pump of the type comprising a plunger that reciprocates vertically in a pump chamber to dispense liquid from a container to which the pump is attached. The pump includes a vent opening to vent air to the interior of the container as liquid is drawn from the container by the pump. The pump plunger locks in its vertically downward position in the pump chamber and is provided with a stopper that plugs the vent opening and prevents liquid in the container from passing through the vent opening when the plunger is in its locked position.
(2) Description of the Related Art
Manually operated reciprocating liquid pumps are typically comprised of a vertically oriented pump chamber having a dip tube extending from its bottom end and a closure cap at its top end employed in attaching the pump to a liquid container. A vertically reciprocating piston is received in the pump chamber and a hollow tubular plunger extends upwardly from the piston to a dispensing head at the top end of the plunger. A spring is positioned between the bottom of the pump chamber and the piston and biases the piston, plunger and dispensing head upwardly. The plunger is manually depressed downwardly and returns upwardly under the bias of the spring when operating the pump to draw liquid from the container interior into the pump chamber and then through the plunger hollow interior and the dispensing head. An example of such a manually operated reciprocating liquid pump is disclosed in the U.S. Patent of Foster et al. U.S. Pat. No. 5,401,148, which is incorporated herein by reference.
Many manually operated reciprocating liquid pumps such as that disclosed in the above-referenced patent are provided with vent openings. The vent openings communicate the exterior atmosphere of the pump with the interior of the container when the pump plunger is reciprocated between its charge and discharge positions. The vent openings allow air to pass through the openings and enter the liquid container to fill the volume in the container interior left vacant by the liquid being dispensed by the operation of the pump. Without such vent openings, as liquid is dispensed from the container a vacuum would be created in the container that would eventually overcome the vacuum created by the pump piston moving to its charge position in the pump chamber, preventing the pump from drawing further liquid into the pump chamber, or could possibly result in the collapsing of the container inwardly on itself.
As disclosed in the above-referenced patent, many vent openings are provided in a sidewall of the pump chamber above the path of travel or the stroke of the pump piston. It has been observed that, with the pump plunger pushed downwardly to its discharge position and locked when not in use, if the container and pump are positioned on their side the liquid filling the container will pass through the vent opening and enter the portion of the pump chamber above the piston. The liquid filling the pump chamber surrounds the exterior surface of the plunger. The next time the pump is prepared for use by unlocking the plunger and permitting the spring to push the plunger out of the pump chamber to the charge position of the piston, residue of the liquid surrounding the plunger above the piston often adheres to the plunger. It is often undesirable to have the liquid product adhering to the exterior surface of the extended plunger where it can come into contact with the user's clothing possibly staining the clothing, and where it gives a generally undesirable appearance to the extended pump plunger.
This problem with prior art manually reciprocated pumps could be overcome if the pump were provided with a mechanism that would close the vent opening when the pump was not in use, thereby preventing the undesirable leakage of liquid through the vent opening into the pump chamber if the pump and container were positioned on their side.